On Tue, Apr 07, 2026 at 11:00:21 -0400, Haines Brown wrote: > >From MAILER-DAEMON Tue Apr 07 10:47:07 2026 > Return-path: <> > Envelope-to: [email protected] > Delivery-date: Tue, 07 Apr 2026 10:47:07 -0400 > Received: from Debian-exim by Iskra.histomat.net with local (Exim 4.96) > id 1wA7hr-0003St-1r > for [email protected]; > Tue, 07 Apr 2026 10:47:07 -0400
This is a message generated locally on your own system. It was not received over the network. The <> is just a notation for the empty string. In other words, the sender address is a zero-length string. It's blank. This is normal for "bounce" messages which are generated to indicate an error (usually that some other message couldn't be delivered). > Auto-Submitted: auto-replied > From: Mail Delivery System <[email protected]> > To: [email protected] > References: <[email protected]> > Subject: Message frozen > Message-Id: <[email protected]> > Date: Tue, 07 Apr 2026 10:47:07 -0400 > > Message 1wA7hq-0003Sn-0C has been frozen (delivery error message). > The sender is <>. > > The following address(es) have yet to be delivered: > [email protected]: SMTP error from remote mail server after pipelined end > of > +data: 554 5.7.1 <>: Sender address rejected: Null Sender Address is > Prohibited I'm not an exim guru, so I don't know exactly what's happening here, but it *appears* that your exim is generating a bounce message, which it cannot deliver for some reason, and then that delivery failure generates another bounce message, which cannot be delivered, and so on. The intended recipient appears to be "[email protected]" (from the Envelope-to: header, and from the third line of the Received: header). I would start by looking at how deliveries to that address have been configured. First question: is "iskra.histomat.net" treated as a local delivery domain, or a remote delivery domain? (This is in your configuration.) Second question: if iskra.histomat.net is local, then is "postmaster" configured as an alias, or as a real account? It should be an alias, and you should be able to see what the alias expands to, if this is in fact a local domain. Third question: why is "Null Sender Address Prohibited"? That would appear, at first glance, to be the underlying cause of the delivery failures. Is this some kind of anti-spam measure you've enabled? (Yes, spammers frequently use null senders. No, that doesn't mean it's a good idea to unilaterally block all messages with a null sender. And if you *do* block them, then you must not generate a bounce message of your own as a result. You must simply discard the message.) Looking at your errors again, it seems you have configured something to perform a remote delivery. Thus, "SMTP error from remote". Perhaps you've got "postmaster" aliased to "[email protected]" and then "histomat.net" (which is different from "iskra.histomat.net") is configured as a remote domain, not local. So, here's my guesswork -- and you should verify all of this yourself. 1) You've got "iskra.histomat.net" configured as a local delivery domain, but NOT "histomat.net". 2) You've got "postmaster" aliased to "[email protected]". 3) The remote system that received messages for @histomat.net addresses is configured to reject messages with a null sender. 4) Your local system is stuck in a loop, because every time it tries to send an error message to postmaster, the error message fails, which triggers another error message, unendingly. If you verify that all of these points are correct, then changing any of them should break the cycle. The most viable changes would be either to re-alias postmaster to a local account instead of a remote address, or to configure the remote mail server to stop rejecting null senders. (Or, I suppose, to re-alias postmaster to a different remote account, which accepts null senders.) If none of those is acceptable, then you'll need someone with in-depth exim experience to recommend alternatives.
